The present invention relates to a concealed slide fastener of the type in which the member normally referred to simply as element is attached along a side edge portion of a woven fabric tape, which is longitudinally double folded with the element projected on the turned-over or concealed side of the folded tape.
Slide fasteners of the type mentioned have been publicly known since before, which individually have a crosssectional configuration or structure as illustrated in FIG. 1 of the accompanying drawings: A pair of woven fabric tapes 1A and 1B respectively have elements 2A and 2B of for example a coil-like structure attached by sewing with threads 3A and 3B along a side edge portion respectively thereof to compose an engageable pair of fastener stringers fA and fB. Elements 2A and 2B respectively have coupling heads 4A and 4B, which are mutually engaged or meshed and tapes 1A and 1B are respectively double folded as illustrated, with the portions 5A and 5B as points of folding, which abut against each other at the engaged point or portion 6 where the elements 2A and 2B are visually concealed when the fastener is attached to clothing or the like.
With the conventional fastener stringers having the above structure, various shortcomings are indicated. For example, it often tends to occur that tapes 1A and 1B are folded with the point of the folding deviated in either side or lateral direction from a reference point or the abutting point 6, so that there becomes a difference produced between the point 6 and the center of the coupling of the heads 4A and 4B as shown in FIG. 1. Otherwise, as shown in FIG. 2, it is difficult to have the fastener tapes 1A and 1B satisfactorily folded or turned over about their respective points of folding 5A and 5B.